Preheat oven to 400°F. Lightly grease a 9×13-inch baking dish.
Steam broccoli until crisp-tender, 3–4 minutes. Drain well and pat dry to avoid a watery casserole.
Whisk soup, mayonnaise, sour cream, broth, lemon juice, curry powder, garlic powder, onion powder, salt, and pepper until smooth.
Spread broccoli in the dish. Scatter chicken over the top, then pour the sauce evenly and gently toss to coat.
Sprinkle cheddar evenly over the casserole.
Stir breadcrumbs with Parmesan and melted butter, then shower the mixture over the cheese.
Bake until bubbly and golden, 22–25 minutes. Let rest 5 minutes before serving.